Selfish intent, plus MySQL is fading...
Would certainly agree with the sentiment that if he wanted to profit from it, he could have chosen not to sell to Sun. But http://www.groklaw.net/article.php?story=20091208104422384 does a pretty good job of hilighting Monty's business motivations. And (as someone that runs an ISP, manages many MySQL instances, and has interacted with MySQL AB's support peeps on behalf of clients), the quality has never been that great. MySQL is a great core for small stuff, but breaks in difficult-to-diagnose ways as you throw more data at it, and the possible tuning parameters are out of this world. The support from MySQL AB for thousands of pounds per server per year is pretty so-so, mostly restricted to responses like "have you tried version X?" and "are you sure the hardware isn't faulty?" and "yes this is an acknowledged bug in this version, I would suggest not using that feature for now". I see more of our customers favouring PostgreSQL, SQLite, (soon) Drizzle, and even so-called "NoSQL" databases like CouchDB where a little forethought can give you an SQL-free application.
It's obviously disheartening to see your life's work become bought up by another company whose motivations will be to choke it, but I think Monty is kidding himself if he thinks that MySQL's continued development is important to anyone but him (and other developers who can't or won't move on to better products). Oracle can't stop everyone using it, but they can keep it on life support for the benefit of MySQL AB's current income stream, all the while selling "upgrades" to their new customers.